Tea leaves are often sold in bags that are made from a porous material and placed in a cup or pot of hot water to infuse. In most cases the bag is removed from the water and prior to drinking the tea.
These bags often contain a significant volume of liquid when they are removed from the infusion liquid. This can make the bags unpleasant to deal with in terms of feeling soggy and tending to drip onto and even stain the user's clothing, table linen etc.
Attempts have been made to overcome or at least alleviate this problem by providing the bags with means for squeezing or wringing at least some of the liquid from the bags after use.
U.S. Pat. Nos. 3,539,355, 3,237,550, 2,881,910, 2,878,927 and 2,466,281 disclose infusion bags having drawstrings that are threaded through holes in the walls of the bag. However, dry infusible material can leak out of the bags prior to use, the holes weaken the structure of the bags thus encouraging them to tear and release their contents, and liquid can leak through the holes during squeezing action.
WO 91/13580 discloses analogous examples in which the drawstring may be retained at desired locations by staples driven through the walls of the bag. This similarly creates leakage paths and local weaknesses at regions where the drawstring tension is likely to be applied the bag.
Further examples of squeezable bags include U.S. Pat. No. 3,415,656, WO 92/06903 and WO 93/19997 which have envelopes formed by two rectangular layers of sheet material that are heat sealed together around their edges. A loop of thread is held in the bag by being trapped in the heat sealed margins at least at one region of those margins remote from one end of the bag where the ends of the loop emerge through the heat sealed margin at that end. This arrangement introduces another potential problem in that the heat seal where the thread is trapped is placed under stress when the bag is contracted and if it fails the bag is opened. Since this is likely to occur at the lower end of the bag, the solid contents would be spilled immediately. It is also noted that these earlier proposals do not suggest how the infusion packages can be economically produced.